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Design of a Lightweight Mounted Tip/Tilt Mirror . Mike Borden OPTI 523 4/6/09. Design Problem 4: Large Mirror Mount. To Do List. Type of lightweight Mirror material and coating Linear actuator Mount and flexure design. Lightweighting. Contoured Back. Sandwich, and Open Back.
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Design of a Lightweight Mounted Tip/Tilt Mirror Mike Borden OPTI 523 4/6/09
To Do List Type of lightweight Mirror material and coating Linear actuator Mount and flexure design
Lightweighting Contoured Back • Sandwich, and Open Back
Mirror Material • Considerations • High stiffness to weight • Ease of manufacture • Minimal thermal stresses • Cost • Main materials being considered • ULE, Zerodur, Fused Silica, Beryllium, Aluminum, BK7
Mirror Material • Possibilities • Pure Beryllium mirror • Expensive and difficult to manufacture • Thermal considerations non-issue • Fused Silica, BK7, Aluminum substrate w/ silver coating • Aluminum w/ silver coating provides smallest ∆𝛂 • (23 ppm / K and 18.9 ppm/ K) • Thermal expansion / contraction an issue • Something crazier – Copper, Brass, Beryllium Copper, Stainless
Optical Specifications • Silver Coating • Meets spectrum requirements
Optical Specifications • Error Budget – 30 nm rms WFE • Mirror surface roughness (∆S) • 20 nm rms • Self weight deflection (δ) • 20 nm rms • Beam diameter • 200 mm diameter mirror accommodates 150 mm beam diameter
Mounting Concept Invar Sleeve Spherical Bearing Micrometer
Remaining Tasks Verify number of supports Reflectance of Be Tolerance bearings for thermal loading Flexure design – dimensions, material FEA analysis of deflection / thermal loading, resonant frequency Linear actuator / micrometer selection